• Journal of Communications and Networks
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• 제16권2호
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• pp.193-201
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• 2014

In cognitive radio networks, the packet transmissions of the secondary users (SUs) can be interrupted randomly by the primary users (PUs). That is to say, the PU packets have preemptive priority over the SU packets. In order to enhance the quality of service (QoS) for the SUs, we propose a spectrum access strategy with an ${\alpha}$-Retry policy. A buffer is deployed for the SU packets. An interrupted SU packet will return to the buffer with probability ${\alpha}$ for later retrial, or leave the system with probability (1-${\alpha}$). For mathematical analysis, we build a preemptive priority queue and model the spectrum access strategy with an ${\alpha}$-Retry policy as a two-dimensional discrete-time Markov chain (DTMC).We give the transition probability matrix of the Markov chain and obtain the steady-state distribution. Accordingly, we derive the formulas for the blocked rate, the forced dropping rate, the throughput and the average delay of the SU packets. With numerical results, we show the influence of the retrial probability for the strategy proposed in this paper on different performance measures. Finally, based on the trade-off between different performance measures, we construct a cost function and optimize the retrial probabilities with respect to different system parameters by employing an iterative algorithm.

• 한국통신학회논문지
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• 제19권5호
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• pp.842-856
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• 1994

광대역 종합정보 통신망 (B-ISDN)이 수용할 여러 서비스들은 다양한 지연, 지연 변화 및 셀 손실 확률 요구 사항을 가지고 있다. B-ISDN을 위한 적절한 제어 방법의 설계는 매우 중요하고 어려운 문제이다. 본 논문에서는, 그러한 다양한 요구사항을 만족하기 위하여, 지연 및 손실 우선 순위 모두를 가진 다종화 알고리즘을 제안한다. 손실 우선 순위의 구현을 위하여, 음성 셀은 폐기 불가한 셀(즉, 높은 우선 순위의 셀) 및 폐기 가능한 셀(즉, 낮은 우선 순위의 셀)로 생성됨을 가정하였다. 낮은 순위의 음성셀은 통신망내에서 혼잡이 발생하면 폐기될 수 있다. 본 셀 탈락 방법은 음성 및 데이터의 지연뿐만 아니라 셀 손실도 감소 시키는 것을 보여주고 있다. 이러한 부하 감소 방법은 광대역 종합정보 통신망의 이용율을 크게 개선 시킬 수 있을 것으로 기대된다.

• 대한전기학회논문지:전력기술부문A
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• 제48권3호
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• pp.234-240
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• 1999

This paper presents a new approach for large-scale generator maintenance scheduling optimizations. The generator preventive maintenance scheduling problems are typical discrete dynamic n-dimensional vector optimization ones with several inequality constraints. The considered objective function to be minimized a subset of{{{{ { R}^{n } }}}} space is the variance (i.g., second-order momentum) of operating reserve margin to levelize risk or reliability during a year. By its nature of the objective function, the optimal solution can only be obtained by enumerating all combinatorial states of each variable, a task which leads to computational explosion in real-world maintenance scheduling problems. This paper proposes a new priority search mechanism based on each generator's discrete sensitivity value which was analytically developed in this study. Unlike the conventional capacity-based priority search, it can prevent the local optimal trap to some extents since it changes dynamically the search tree in each iteration. The proposed method have been applied to two test systems (i.g., one is a sample system with 10 generators and the other is a real-world lage scale power system with 280 generators), and the results anre compared with those of the conventional capacith-based search method and combinatorial optimization method to show the efficiency and effectiveness of the algorithm.

• KIEE International Transactions on Power Engineering
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• 제5A권3호
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• pp.260-268
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• 2005

This paper proposes an improved investment pnonty decision method of facilities considering the reliability of distribution networks. The proposed method decides an investment order of the facilities combining, by fuzzy rules, the investment priority decision by KEPCO and that by reliability evaluation indices. The reliability evaluation indices are SAIFI (System Average Interruption Frequency Index) and SAIDI (System Average Interruption Duration Index). The reliability analysis method of distribution networks applied in this paper utilizes the analytic method, where the used reliability data is the historical data of KEPCO. Particularly, we assumed that the failure rate increases as the equipment ages. To verify the performance of the proposed method, we applied it with the planned projects to reinforce the weak electrical facilities in KEPCO in 2004. The evaluation result showed that, under a limited budget, the reliability of KEPCO in the Busan region using the proposed method could be enhanced if used rather than the conventional method typically in place. Therefore, the results verify that the proposed method can be efficiently used in the actual priorities method for investing in the electrical facilities.

• 품질경영학회지
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• 제42권1호
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• pp.43-61
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• 2014

Purpose: This study identifies preventive measures for VOC management by analyzing the causes and effects of factors that contribute to high risk service failure using FMEA on KORAIL VOC data. Methods: Two research methods were used. First, a Risk Priority Number (RPN) was assigned to each KORAIL VOC based on Failure Mode and Effect Analysis (FMEA). Second, multiple regression analysis was run with RPN factors that include severity, occurrence, and detection as the independent variables and customer dissatisfaction as the dependent variable. Results: Multiple regression analysis showed that RPN factors including severity, occurrence, and detection had significantly positive relationship with customer dissatisfaction. Based on these results, an FMEA was performed on VOC categories with high RPN for railroad stations including platform, ticketing, ticket verification, parking, and escalator, and VOC categories with high RPN for trains including entrance doors, cafes, air quality, announcement, and ticket verification. Conclusion: This study has practical implications to service failure management. A priority order using FMEA was established for the list of customer dissatisfactions that should be addressed to actively manage service failure, and strategies for tackling this priority list are offered.

• 한국물환경학회지
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• 제23권4호
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• pp.440-447
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• 2007

This paper is dealing with recent hot issues related with copper toxicity and its criteria, which was caused by a new government policy relocating some industries discharging priority-water quality pollutants from the watershed of Han River to other regions. Author is not interested in arguments between two sides of anti- and pro-policy but would like to go over status of copper pollution and its management and regulatory policy in Korea. From the data of published Research Journals and Reports, it can be concluded that copper is very common metal not only in the effluent from publically owned wastewater treatment plants, but also as a non-point source pollutant in the rainfall runoff. In addition, there have been very few studies personal interests, not by National Fund Basis. In order to enforce a new regulation, national-wide macro and micro-mass balance work of heavy metals should be performed in advance. In particular, background concentration and measurement errors have to be clearly defined before a new standard or criteria is established. The new standard has to be acceptable in terms of the best available technology and cost.

• 한국환경복원기술학회지
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• 제22권4호
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• pp.65-80
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• 2019

The Wetland Conservation Plan is used as a tool to set the management direction of wetland protected areas, and which is establishing a plan for the conservation, wise-use, and management based on wetland's condition. This study was conducted to establish a conservation plan considering the functions and management conditions of Upo wetland protected area. To this end, there are analyzed the current issues, plans and implementation status of Upo Wetland Conservation Plans in the past. The management elements to be considered in establishing the Wetland Conservation Plan were selected through prior research analysis and the priority of those elements was identified through the AHP. As a result, it was found that lack of considering the changes and performance evaluation of the existing plans in wetlands, conducting short-term projects related to maintenance original function of wetland, different management methods for wetland protected areas and other adjacent areas, lack of understanding and cooperation by stakeholders, inconsistencies in timing of the Conservation Plan and survey of wetland protected areas. In order to improve the problem, it needs to include the performance evaluation stage of establishing the conservation plan, strengthen cooperation of stakeholders and expertise, continuing of projects for wetlands' maintenance, priority of the project considering the management side, and to adjust the timing of plans to improve data availability.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 춘계학술대회
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• pp.469-472
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• 2014

S-MAC은 패킷 교한을 조정하고 idle listening을 줄이기 위해 로컬 sleep-wake 스케쥴을 사용하는 CSMA와 TDMA의 하이브리드 방식이다. 이 기법에서는 모든 노드들이 동일한 우선순위를 가지고 있기 때문에 트래픽의 양이 많은 경우 지연시간이 증가된다. 본 논문에서는 실시간 음성 스트리밍과 같은 어플리케이션에 적합한 처리량과 진송지연을 제공할 수 있는 트래픽 적응적 MAC 프로토콜을 제안한다. 제안된 프로토콜에서는 실시간에 적합한 성능을 제공하기 위해 (m,k)-firm 스케쥴링 기법을 이용한 우선순위 개념을 사용한다. 성능 평가를 위해 다양한 노드 수에 대해 패킷 전송률과 노드의 평균지연시간을 시뮬레이션을 수행했다.

• 한국보육지원학회지
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• 제20권3호
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• pp.1-18
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• 2024

Objective: The purpose of this study was to investigate and analyze the needs of early childhood teachers in order to improve their competencies for Education for Sustainable Development (ESD). Methods: Two hundred fifty-four early childhood teachers working in the B area responded to a questionnaire developed by the researcher, assessing the importance and performance of various competencies. The data were analyzed using the Borich demand model and the Locus for Focus model. Results: First, in terms of educational needs by category, the competency to implement ESD was identified as the highest priority, followed by understanding the value of ESD and the economic aspects of ESD content. Second, 17 items were identified as the top priority for educational needs in each detailed item, and 6 items were identified as the next priority. Conclusion/Implications: By directly analyzing the needs of early childhood teachers to improve their competencies for ESD, this study was able to identify the competencies required to enhance ESD for young children. Additionally, it provided a basis for discussing the direction of teacher education for early childhood teachers in the context of ESD.

• 기술혁신학회지
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• 제17권1호
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• pp.195-218
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• 2014

최근 글로벌 경제위기와 저성장기조의 장기화로 많은 국가에서 경제성장을 위한 중요정책으로 창조경제를 제시하고 있다. 우리나라도 핵심 정책으로 창조경제를 통한 창조산업 육성과 창업활성화, 일자리 창출 등을 주요 정책으로 추진하고 있다. 그러나 국가마다 창조경제에 대한 정의와 추진하는 세부분야가 상이하며, 국가산업단지의 창조경제 및 창조산업 활성화 방안에 관한 연구는 부족한 실정이다. 본 연구에서는 70년대 이후 국가경제에서 중요한 축을 담당하고 있는 구미국가산업단지를 중심으로 창조클러스터로 발전하기 위한 발전방안의 우선순위 및 중요도를 AHP분석을 통해 도출하였다. 분석결과 창조성 촉진 요인이 우선순위가 가장 높게 나타났으며, 창조인프라, 창조네트워크 순으로 나타났다. 이와 같은 결과는 국가산업단지가 국가경제를 지속적으로 견인하기 위해서는 창조성을 촉진하여야 하며, 이를 위해서 창조적 인재양성과 창조적 R&D의 확대가 우선하여야 한다는 것을 의미한다. 본 연구는 국가산업단지를 창조클러스터로 발전시키기 위한 방안을 인프라 등의 하드웨어와 소프트웨어 정책 모두를 반영하여 우선순위를 도출함으로써 정부 및 지역 정책입안자들과 혁신기관에게 성공적인 창조클러스터 구축을 위한 기초자료와 실질적인 정책 가이드로 활용될 수 있다.